gridSpacing/unitSI: as in axisLabels

Apply changes as approved in last VC :)

STANDARD.md

@@ -431,15 +431,17 @@ on Unit Systems and Dimensionality, further below):
 
   - `gridUnitSI`
     - type: 1-dimensional array containing N *(float64 / REAL8)*
-            elements, where N is the number of dimensions in the simulation. Dimensions shall be ordered from slowest to fastest varying index of the described mesh.
+            elements, where N is the number of dimensions in the simulation.
+            The order of the N 7-value arrays must be identical to the axes in `axisLabels`.
     - description: unit-conversion factor to multiply each value in
                    `gridSpacing` and `gridGlobalOffset`, in order to convert
                    from simulation units to SI units
     - example: `(1.0e-9, 1.0e-9, 1.0e-6)`
 
   - `gridUnitDimension`
     - type: array of 7 N *(float64 / REAL8)*
-            elements, where N is the number of dimensions in the simulation. Dimensions shall be ordered from slowest to fastest varying index of the described mesh.
+            elements, where N is the number of dimensions in the simulation.
+            The order of the N 7-value arrays must be identical to the axes in `axisLabels`.
     - description: powers of the 7 base measures characterizing the
             grid axes's dimensions (length L, mass M, time T,
             electric current I, thermodynamic temperature theta,